The application of a counting device to filtering jugs, for counting the filtering cycles which take place between each replacement of the cartridge in order to establish and indicate to the user that the cartridge is exhausted when the count indicates that the maximum number of permissible filtering cycles for that cartridge has been reached is known. Generally the counting device is on a lid of the filtering jug. It is also known that such counting may be incorporated with auxiliary counting of the elapsed time between first activation of the cartridge, because in addition to quantitative deterioration through the effect of the total quantity of water processed, the filtering material is also subject to a temporal deterioration over time through the effect of the time which has elapsed since the first use (activation) of the cartridge.
Finally it is known that the filter cartridge (and the filtering material in general) is subject to a “temporary” deterioration of filtering efficiency in relation to the number of filtering cycles performed in the course of a day. This temporary deterioration derives from temporary saturation of the filtering material, which requires a rest time between filtering cycles in order to regenerate itself in order to ensure maximum filtering efficiency throughout the service life of the same. Because of this requirement it is currently provided that a maximum number of permissible daily filtering cycles for satisfactory performance of the filtering jug is recommended in the operating instructions for filter cartridges and/or filtering jugs.
In jugs for filtering drinking water it is however typical that the filtering vessel is filled by different users in the course of the day, for example by the person who uses up the filtered water and therefore refills the jug before placing it back in the refrigerator. It is therefore possible that the number of daily filtering cycles may be exceeded without the users being at all aware of it.
There is also the fact that the maximum number of daily cycles has an influence on the maximum permissible number of cycles for a cartridge, because if the counting means intended to monitor the cartridge are limited to monitoring of the cycles performed they may indicate a number of residual cycles available which is greater than the actual number of cycles available bearing in mind the limitation consequent upon the days available and the maximum number of daily cycles available before the cartridge loses efficiency.